This valve provides independently actuatable outputs with condition responsive means insuring sufficiency of fluid feed to a priority function.
In a hydraulic system serving multiple functions, it is usually impracticable to use a pump large enough to supply a maximum possible demand of the system. It is, therefore, sometimes necessary to provide an order of priority to insure adequate flow to a certain function which requires precedence, such as a steering function of a mobile unit. An example of a priority flow valve which supplies such priority flow to a priority function and secondary flow to a secondary function, when the priority flow requirements are satisfied or the priority flow path is blocked, is described in U.S. Pat. No. 3,979,908 granted to Loren L. Alderson, a joint inventor of the present invention. The priority flow valve described in U.S. Pat. No. 3,979,908 requires a pump having a capacity at least equal to maximum demand of the priority function, even when such peak demands are of short duration. A smaller pump can satisfy short term priority peaks if supplemented by stored power from an accumulator. The present invention is a priority flow valve which can use such stored power, when necessary, thus permitting a smaller pump to serve a system having short term priority demand peaks.